FIG. 5 shows a configuration of a vehicle speed control apparatus described in a Patent Document 1. In FIG. 5, a reference sign 1 denotes an acceleration force calculating section which calculates a command side acceleration force by a differential value of a vehicle speed command Vs×vehicle mass (a vehicle weight M). A running resistance is calculated in accordance with a detected vehicle speed V by means of a running resistance calculating section 2. The acceleration force and the running resistance are added at an addition section 3, then a driving force command F required for achieving a target driving mode is calculated.
This driving force command F is inputted to a feed-forward controller 4 (a driving force characteristic map, namely, a map in which a driving force characteristic is previously recorded before a mode pattern driving) together with the vehicle speed command Vs. The feed-forward controller 4 outputs an accelerator opening angle command θFF in accordance with the map.
In addition, an addition section 5 detects a deviation between the vehicle speed command Vs and an actual vehicle speed V. A vehicle speed deviation correction calculating section 6 performs a correction calculation of the vehicle speed deviation. Then, the corrected vehicle speed deviation and the driving force command F are added at an addition section 7. Further, a detection side acceleration force calculating section 8 calculates an acceleration force by a differential value of vehicle speed V×the vehicle mass. At an addition section 9, the acceleration force and the running resistance are added, then a driving force of the detection side is calculated.
An addition section 10 calculates a deviation between the driving force of the command side and the driving force of the detection side, and this deviation is inputted to a feedback controller 11. The feedback controller 11 outputs an accelerator opening angle command θFB. An addition section 12 adds θFF and θFB, then an accelerator opening angle command θ is obtained.
The accelerator opening angle command θ is inputted into a virtual vehicle 13. The virtual vehicle 13 generates an engine driving force required for the driving mode according to the accelerator opening angle command θ. The virtual vehicle 13 is configured by a vehicular driving force characteristic section 14 including the engine, an addition section 15 and a vehicle speed calculating section 16. The addition section 15 subtracts the running resistance from the driving force that is generated from the driving force characteristic section 14, and the vehicle speed calculating section 16 calculates the vehicle speed.
FIG. 6 is a configuration in which a vehicle speed feedback gain correction by means of a weight (M) 17 is added to the vehicle speed deviation correction calculating section 6 in the vehicle speed control apparatus in FIG. 5.    [Patent document 1] a Japanese Patent Application Publication (tokkai) No. 2005-297872